The integration of an illumination device with an imaging device to increase the light available for imaging an object has a number of problems associated with it, particularly in the case of integrating the illumination and imaging devices within a point-of-sale (POS) barcode scanner.
One solution to such an integration is to place the illumination device and the imaging device on opposite sides of a window, or platen. This has the problem that the user, be that the check-out operative or the customer in the case of a POS barcode scanner, is subject to bright lights which may be strobing due to the illumination device operating only when an image is recorded. Such strobing can occur either directly or by reflection from the window. The propensity of strobing lights to bring about epileptic seizures is well known.
An alternative solution to placing the illumination device on opposite sides of the window is to have them placed on the same side of the window with the object to be imaged on the other side. Whilst reducing the likelihood of user dazzle by the illumination device, this arrangement has a number of problems associated with it. Firstly, a proportion of the light emitted from the illumination device is reflected back from the surface of the window and will enter the aperture of the imaging device, such that it saturates the imaging device. This leads to a singularity in the image, associated with the reflection, where no feature of the object is discernable. Accordingly the barcode can be unreadable, causing the object to have to be rescanned.